Tungsten hexachloride is used as a catalyst, in the chemical vapor deposition of tungsten, and in the production of high purity fine particle size tungsten metal powder.
Tungsten hexachloride (WCl.sub.6) is typically produced by passing chlorine (Cl.sub.2) over a quartz boat filled with tungsten powder condensed and collected as powder at the exit end of the reaction furnace. When the tungsten powder in the boat is completely consumed by the reaction, the quartz furnace tube must be opened to replace the empty boat with a filled one. There are several disadvantages in using tungsten powder for the feed material. First, the powder must be placed in a suitable container in order to be effectively stoked into the hot zone of the furnace tube. Quartz boats are typically used since quartz resists attack by chlorine at high temperature. However, the boats are fragile and will gradually deteriorate so that they must be frequently repaired or replaced. A second disadvantage is that the reaction rate is slow. The production rate for tungsten hexachloride seems to be primarily dependent on the amount of tungsten surface area exposed to the flowing chlorine in the furnace tube. Since the powder is contained in a boat, only the top surface is available for reaction. Finally since the furnace tube must be opened frequently to replace empty boats, the tungsten hexachloride product can easily be contaminated by oxygen, forming tungsten oxychloride. To reduce the oxygen content of the product it must be boiled and recrystallized. This reduces the yield since some tungsten oxychloride escapes during the boiling of pure tungsten hexachloride. Minimizing the oxygen contamination increases the formation of pure tungsten hexachloride.
It would be desirable to produce tungsten hexachloride without the above disadvantages.